Is My Energy Direct Debit Correct? UK Calculator
Use this calculator before accepting a direct debit increase or asking for a reduction. It turns the supplier’s forecast, balance and buffer logic into a number you can challenge in writing.
Energy direct debit calculator
The £1,800 default is illustrative. An annual average can understate a winter-only period: enter the supplier’s forecast for those specific months if available. Balance adjustments are spread over your selected months.
Enter your numbers to compare.
This is a sense-check. It does not reproduce any supplier’s internal forecast model and is not financial or legal advice.
The short answer
A fair direct debit is not just annual cost divided by 12. It should also reflect current credit, account debt, recovery period, seasonal buffer and the supplier’s latest forecast. Use this calculator to see whether the proposed amount is broadly plausible or needs a written challenge.
What number should I enter?
| Input | Use this | Avoid this mistake |
|---|---|---|
| Annual forecast | Use a recent annual estimate or actual annual cost if reliable. | Do not use one abnormal winter bill as a full-year forecast. |
| Credit | Use credit that still exists after the latest bill. | Do not count credit that has already been spent by new charges. |
| Debt | Use account debt the supplier is trying to recover. | Do not mix genuine debt with a disputed old balance without checking it. |
| Buffer | Use a modest end-of-year buffer. | Do not accept a large unexplained buffer without asking why. |
| Months | Use the period the supplier says it is smoothing over. | Do not assume it is always 12 months. |
When the payment looks too high
- Ask for the annual usage forecast.
- Ask how current credit or debt was used.
- Ask what buffer they are holding and why.
- Ask for the next review date.
When the bill may be the real issue
- Wrong or estimated reading.
- Back billing or old charges.
- Smart meter stopped sending readings.
- Tariff or standing charge changed.
Direct debit challenge wording
Please explain how my proposed direct debit of £[amount] was calculated.
In particular, please confirm the annual usage forecast, current account balance, any debt recovery amount, the buffer being held and the review period used.
Based on my calculation, a reasonable monthly amount appears closer to £[your figure].
If you disagree, please provide a written breakdown showing why the higher amount is necessary.
How a fair direct debit is actually calculated
A direct debit is not the bill. It is a payment plan designed so that your account lands near zero at the end of the year, having carried you through a winter that costs far more than a summer. That means five numbers, not one:
monthly = ( forecast annual cost − current credit + debt being recovered + target buffer ) ÷ months
Every argument about a direct debit is an argument about one of those five terms. Working out which one is the problem is most of the job.
Worked from the Ofgem cap, July–September 2026
This example uses 2,700 kWh electricity and 11,500 kWh gas at July–September 2026 average rates for 365 days. These are older consumption assumptions; the revised Ofgem typical-use headline was £1,663. Use your own usage, balance and current tariff for a payment check.
| Line | Calculation | Cost |
|---|---|---|
| Electricity units | 2,700 × 26.11p | £704.97 |
| Electricity standing charge | 365 × 57.19p | £208.74 |
| Gas units | 11,500 × 7.33p | £842.95 |
| Gas standing charge | 365 × 29.04p | £106.00 |
| Forecast annual cost | £1,862.66 | |
| Monthly, no debt, no buffer | £1,862.66 ÷ 12 | £155.22 |
For this illustrative household, with a zero balance, roughly £155 a month is the calculated estimate. If your usage is typical, your balance is around zero, and the supplier is asking for £230, then about nine hundred pounds a year is going somewhere — into a forecast that assumes higher usage, into debt recovery, or into a buffer. They should be able to say which.
Standing charges are 17% of that bill. £314.74 a year before a single unit is used. That is why “I barely use anything, why is it so high” usually has an answer, and why cutting usage moves the number less than people expect. See standing charges explained.
Cap rates shown are averages for direct debit customers in England, Scotland and Wales, including VAT, for 1 July to 30 September 2026. Your region and payment method change them — use the rates on your own bill with the direct debit calculator.
What the supplier is actually obliged to do
This is worth knowing because it changes the question you ask. You are not asking for a favour.
- Set the payment on the best and most current information available. Ofgem's supply licence rules require suppliers to base fixed direct debits on the best information they have — not on a stale estimate, and not on a figure chosen to build a cushion. If they are billing you on estimates while holding six submitted readings, that is the argument.
- Explain the basis of the payment when asked. A supplier that responds to a direct request for the calculation with “your usage has increased” has not answered it.
- Refund a credit balance when you ask, unless it is fair and reasonable in the circumstances not to. “We hold it for winter” is a reason that needs to be justified against your actual forecast, not asserted.
- Not use debt recovery invisibly. If part of the monthly payment is clearing arrears, that is a separate thing from the ongoing cost and should be identified as such.
None of that requires you to be aggressive. It requires you to ask five specific questions and put the answers next to your own arithmetic.
The five questions, and what each answer tells you
| Ask | Good answer | Answer that means you have found the problem |
|---|---|---|
| What annual usage forecast did you use, in kWh? | A kWh figure close to your actual last 12 months. | A figure well above your actual usage, or one based on estimated reads, or no figure at all. |
| What is my current balance, and is it credit or debt? | A number that matches your account screen. | A balance that does not match, or one that ignores a recent payment. |
| How much of the monthly amount is debt recovery? | A stated amount and a stated recovery period. | “None” — when the payment is far above your forecast ÷ 12. |
| What buffer are you holding, and why that amount? | A modest figure tied to your winter forecast. | A large unexplained cushion, or a buffer being rebuilt while you are already in credit. |
| Over how many months are you smoothing this? | 12 months, or a stated shorter recovery period. | Six months doubles the balance-recovery part compared with twelve; it does not double ongoing energy use. |
That last row catches a surprising number of cases. A supplier recovering a £600 shortfall over six months rather than twelve adds £50 a month, and nothing on the account screen says so.
The letter that gets an actual calculation back
Copy, fill in the brackets, send by email or the complaints form
The part that does the work is the paragraph with your own numbers in it. A request for an explanation can be answered with reassurance. A request that puts a rival calculation on the table has to be answered with arithmetic.
Frequently asked questions
Can this calculator prove my supplier is wrong?
No. It is a sense-check. It helps you ask better questions about forecast, credit, debt, buffer and review period.
Why did my supplier increase my direct debit if I am in credit?
They may be forecasting higher future use or trying to hold a buffer. Ask for the calculation and current balance treatment in writing.
Should I cancel the direct debit?
Do not cancel without understanding consequences. First ask the supplier to explain and review the amount in writing.
What should my direct debit be for a typical UK home?
On the Ofgem cap for July to September 2026, an illustrative 2,700 kWh of electricity and 11,500 kWh of gas costs £1,862.66 a year, which is £155.22 a month with a zero balance. Your own figure moves with your region, payment method, usage and balance — so ask for the supplier’s calculation rather than treating this illustration as a threshold.
Is the price cap a cap on my bill?
No, and this is the most common misunderstanding in UK energy. The cap limits the unit rate and standing charge, not the total. Use twice as much energy and you pay roughly twice as much, cap or no cap.
Can they raise my direct debit without telling me?
They must notify you of a change. What they frequently do not do is explain how it was calculated — and that explanation is what you are entitled to ask for and what this page is built around.
Should I just cancel the direct debit?
No. Cancelling usually loses the direct debit discount, can move you to a higher standard-credit rate, and turns a billing conversation into an arrears one. Ask for the calculation, propose your own figure, and escalate through the complaints process if they will not engage.
Official sources used for this page
BillDecoded translates official process and billing information into practical checks. It is not affiliated with the Ombudsman, Ofgem, Citizens Advice, Which? or any supplier.